caddyhttp: add replacer placeholders for escaped values

[Qusic]

basically this brings back this v1 change #470

adding uri_escaped, path_escaped, query_escaped being the url.QueryEscaped version of original values

useful for such cases: https://caddy.community/t/how-to-percent-encode-request-url-when-redirecting/30982

[CLAassistant]

All committers have signed the CLA.

[mholt]

Thanks, I was actually curious though, should we do something like {%path}? That almost makes it clearer that it's URI escaping in particular. (as opposed to \ escapes or something).

[francislavoie]

@mholt I agree for the shortcut, but the long form should probably just be plain English to make sure we don't run into issues with regex character sets not including those special characters etc.

[mholt]

That's a good point.

[mholt]

Great - thanks!